William Conrad is credited as "Julius Krelboyne". He was under contract with CBS, so when he appeared on other networks, he generally used this pseudonym.

Probably uncredited because he was about to star over on CBS Radio in Gunsmoke at that time. That was after, Escape...
Romance. August 6, 1951. CBS net. "Pagosa". Sponsored by: Spearmint Gum. Broadcast about one year before the start of the "Gunsmoke" series, this program was written by the author of many Gunsmoke scripts and featured many of the actors who would become regulars on "Gunsmoke." William Conrad plays the role of Jeff Spain, who comes to a small western town and becomes the sheriff. This is a significant broadcast, as the script and characters obviously were the inspiration for "Gunsmoke." This therefore, is possibly the first "adult western!" John Meston (writer), William Conrad, Norman Macdonnell (producer, director), Georgia Ellis, Will Wright, Herb Ellis, William Johnstone (narrator), Tony Barrett, Lamont Johnson, Tom Holland, Junius Matthews, Alexander Courage (music supervisor). 29:39. Audio condition: Very good to excellent. Complete. [RadioGoldIndex]
He was one of the greatest West Coast, Los Angeles,
Radio Actors of all time.
Credits mostly!
http://radiogoldindex.com/frame1.html
http://radiogoldindex.com/cgi-local/p4.cgi?ArtistName=Conrad,%20William&ArtistNumber=49585

GREAT SHOW! A very clever premise with a hero who does not wear a physical mask BUT masks his voice...Like other heroes with a secret id serious problems arise....
A solid cast of pros made each episode very exciting...Now for my puzzler on several episodes there was the unmistakeable voice of William Conrad but no credit for him at the end??? Conrad was certainly a big enough actor (at that point) to get proper billing?..Unless he was appearing under another name an alias?...

I have been listening to otr since I was 8 years old and I'm only 35. I have always been a fan of the crime/mystery/thriller shows. The whisperer is definately a hidden gem like so many other radio shows that lasted only a season or two I.e: murder at midnight, dark fantasy or the haunting hour. Creepy voice and decent plots. This show was definitely overlooked back in the day. Highly recommended.

To bad NBC did not want to pick this show up after the summer of 1951. I found all 13 episodes quite intriguing.